This invention relates in general to device useful in remotely controlled actuation systems and, more specifically, to an electro-optic power cell for use in a fiber optic system for controlling remote electrical devices.
In the past, devices such as aircraft to ship control surfaces, valves, machines and the like were generally controlled from a distance by mechanical linkages or hydraulic systems. While these systems are effective, they are heavy, occupy considerable space and redundant control paths for safety are difficult to provide.
Recently, systems have come into use which use electrical signals passing through wires from input means to control devices. These systems are much lighter in weight, occupy little space and provide redundant wiring paths to protect against loss of control if one wire is damaged. These so-called "fly-by-wire" systems have been found to be very effective in military aircraft and missile systems.
Unfortunately, these systems are subject to power failures, short circuits or other damage to the wires, electromagnetic interference (EMI) from nearby wiring or electrical devices are potentially subject to destruction by electromagnetic pulses (EMP) from nuclear blasts or other sources. These is a particular need to overcome these problems in military aircraft, missiles and ship and in numerically controlled machine tools and where EMI and EMP pose serious problems.
Recently, considerable interest has developed in using optical fiber systems for remote control application and for transmitting information rapidly and accurately over long distances. Fiber optics have many of the advantages of the fly-by-wire systems while being impervious to electrical short circuits, EMI and EMP. Typical fiber optic control systems are disclosed by Sichling in U.S. Pat. No. 4,346,478 and Blackington in U.S. Pat. No. 4,313,226. While these systems are effective they are electrically complex and are not fully protected against system degradation caused by contamination of the optical interfaces.
In my copending U.S. patent application, Ser. No. 07/395,589, filed 8/18/89, I describe an improved fiber optic control system which is capable of fully proportional and easily reversible control. This system, for optimum utility, requires components which are compact, reliable, resistant to contamination and capable of performing varied functions. Prior devices for transducing light energy to a corresponding electrical signal tend to be single-purpose, heavy and complex, and to be subject to performance degradation by outside contaminants, such as moisture and dirt, penetrating between optical and optical-electrical components. Prior photo diode assemblies tend to produce a lower output voltage than required for many applications, requiring that a number of photo diode based conversion cell be wired in series.
Thus, there is a continuing need for improved devices for converting light energy to electrical energy in an accurate and reliable manner, which are resistant to outside contamination, EMI and EMP, and are adaptable to a number of different output requirements.